A secured access entry is effective to prevent unauthorized entry only to the extent that an intruder is unable to reconstruct any authorized entry means of access such as a key, a combination, a password, etc. If the entry means is relatively simple to enhance the performance of an authorized entrant it is too often ascertained by an unauthorized entrant for unauthorized entry. On the other hand a sophisticated complicated entry means may inadvertently defeat even the authorized entrant. It is necessary to devise an entry authorization system for entry that is friendly to authorized entrants and yet able to defeat unauthorized entry attempts.
In another aspect the entry means may operate by a transmission of passwords over an insecure transmission facility. The protection afforded may be compromised by interception of this information by an unauthorized recipient.